Method for manufacturing a laminate, method for manufacturing an electronic component including the manufacturing method, silver paste, and coated silver powder

Abstract

This invention provides a technology that can suppress the diffusion of silver ions from silver powder to a substrate in a process of forming a silver film by heat treatment of silver powder containing a predetermined amount of phosphorus. [Solution] The present invention discloses a method for manufacturing a laminate comprising a substrate and a silver film on the substrate. This manufacturing method includes applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A, which is a barium compound, to the substrate, and heat-treating the substrate, the silver powder and additive A applied to the substrate to form a silver film on the substrate.

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing a laminate, a method for manufacturing an electronic component including the manufacturing method, a silver paste, and a coated silver powder. [Background technology]

[0002] Japanese Patent Publication No. 2005-268164 discloses a conductive coating composition for forming internal electrodes of a ferrite multilayer chip inductor. This conductive coating composition is characterized by the addition of at least one salt or amide of a higher fatty acid. The publication states that electrodes formed on a ferrite layer using this conductive coating composition have appropriate adhesion to the ferrite layer before firing, and are peeled off almost completely and smoothly from the ferrite layer upon firing. Therefore, it is possible to almost completely prevent fluctuations in self-inductance due to the effects of magnetic strain, as well as prevent the occurrence of defects such as cracks during firing.

[0003] Japanese Patent Publication No. 3414502 discloses a high-temperature firing-compatible precious metal powder. This high-temperature firing-compatible precious metal powder is characterized by being obtained by coating the surface of the precious metal powder with a compound of a metal other than the precious metal and an organic acid, and then heat-treating it in an inert atmosphere. The publication states that, with respect to the high-temperature firing-compatible precious metal powder, coating the surface of the precious metal powder with another metal compound reduces the surface area of ​​the exposed precious metal, thereby suppressing the reaction between the precious metal powder and oxygen in the atmosphere. As a result, when the high-temperature firing-compatible precious metal powder is dispersed in an organic vehicle, it is possible to produce a paste for thick-film conductors that prevents various structural defects.

[0004] The conductive paste disclosed in Japanese Patent Publication No. 4126698 contains a silver-based conductive metal powder that is applied to form a pattern on a green sheet mainly composed of glass and oxide ceramics. This conductive paste is characterized by the addition of one or more barium compounds selected from fatty acid barium salts in an amount of 0.16 to 1% by weight relative to the barium metal, and one or more calcium compounds selected from fatty acid calcium salts in an amount of 0.10 to 0.20% by weight relative to the calcium metal, in combination with the conductive metal powder. The publication states that this configuration provides good conductivity, and when printed on a glass-ceramic green sheet and fired, it can reduce warping and deformation of the ceramic multilayer substrate, increase the product yield rate, eliminate defects such as low wiring and disconnections, and improve reliability.

[0005] The coated copper powder disclosed in Japanese Patent Publication No. 6433351 comprises copper powder and a coating for the copper powder. The copper powder contains 140 to 630 ppm of phosphorus as an impurity. The coating contains an organometallic compound of at least one alkaline earth metal from among magnesium, calcium, strontium, and barium. This coated copper powder is characterized in that the concentration of the alkaline earth metal is less than 1.8 times the concentration of phosphorus contained in the copper powder. The publication states that when a copper conductive film is formed using the coated copper powder, the alkaline earth metal forms a compound with the impurities contained in the copper powder when a firing treatment is applied. As a result, the reaction between copper and these impurities is suppressed during the firing process, and a highly conductive copper conductive film can be obtained.

[0006] The conductive paste disclosed in Japanese Patent Publication No. 2019-36435 comprises conductive powder, a binder resin, and an organic solvent. In this conductive paste, the organic solvent has a Fedors solubility parameter of 9.0 (cal / cm³). 3 ) 0.5 The first solvent is as follows, and Fedors' solubility parameter is 10.0 (cal / cm³). 3 )0.5 The above is a mixed solvent containing the second solvent. The Fedors solubility parameter of the organic solvent is 9.0 (cal / cm³). 3 ) 0.5 More than 10.1(cal / cm 3 ) 0.5 The following is stated in the publication: The first solvent is useful for suppressing the occurrence of sheet attack, but when used alone, it is prone to the permeation of conductive powder. The second solvent is useful for suppressing the permeation of conductive powder, but when used alone, it is prone to causing sheet attack. Furthermore, according to the technology described in the same document, by suitably exhibiting the advantages of the first solvent and the second solvent, it is possible to suitably form an electrode in which both the occurrence of sheet attack and the permeation of conductive powder are suppressed. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2005-268164 [Patent Document 2] Patent No. 3414502 [Patent Document 3] Patent No. 4126698 [Patent Document 4] Patent No. 6433351 [Patent Document 5] Japanese Patent Publication No. 2019-36435 [Overview of the project] [Problems that the invention aims to solve]

[0008] The inventors have found that when silver powder contains phosphorus as an impurity, and a silver paste containing such silver powder is fired to form a silver film, silver ions tend to diffuse from the silver film into the substrate, and that the higher the content of the impurity (in this case, phosphorus), the greater the tendency for silver ions to diffuse.

[0009] In view of such circumstances, the inventor of the present invention desires to suppress the diffusion of silver ions from silver powder to a substrate in a process of forming a silver film (fired film) by subjecting silver powder containing a predetermined amount of phosphorus to a heat treatment.

Means for Solving the Problem

[0010] According to the technology disclosed herein, a method for manufacturing a laminate including a substrate and a silver film on the substrate is disclosed. This manufacturing method includes applying, onto the substrate, silver powder containing 50 ppm or more and 500 ppm or less of phosphorus as an impurity and an additive A which is a barium compound, and subjecting the substrate, the silver powder, and the additive A applied onto the substrate to a heat treatment to form a silver film on the substrate. According to such a configuration, in a process of forming a silver film (fired film) by subjecting silver powder containing a predetermined amount of phosphorus to a heat treatment, the diffusion of silver ions from the silver powder to the substrate can be suppressed.

[0011] According to the technology disclosed herein, a method for manufacturing an electronic component is provided. This manufacturing method includes the above-described method for manufacturing a laminate. According to such a configuration, an electronic component in which the diffusion of silver ions to the substrate is suppressed can be provided.

[0012] According to the technology disclosed herein, a silver paste is provided. The silver paste contains silver powder containing 50 ppm or more and 500 ppm or less of phosphorus as an impurity, a resin binder, an organic solvent, and an additive A. The additive A is a barium compound. According to such a configuration, in a process of forming a silver film (fired film) by subjecting silver powder containing a predetermined amount of phosphorus to a heat treatment, the diffusion of silver ions from the silver powder to the substrate can be suppressed.

[0013] According to the technology disclosed herein, coated silver powder is provided. The coated silver powder includes silver powder containing 50 ppm or more and 500 ppm or less of phosphorus as an impurity, and a coating portion containing a barium compound on the surface of the silver powder. According to such a configuration, in the process of forming a silver film (fired film) by subjecting silver powder containing a predetermined amount of phosphorus to heat treatment, diffusion of silver ions from the silver powder to the substrate can be suppressed.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view of the multilayer chip inductor 1. [Figure 2] FIG. 2 is an image of Example 21. [Figure 3] FIG. 3 is an image of Example 24.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the technology disclosed herein will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the technology disclosed herein can be understood based on the technical content taught in this specification and the general technical common sense of those skilled in the art in this field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the technical common sense in this field. In addition, the description of A to B (A and B are arbitrary numerical values) in this specification and the claims means A or more and B or less, and also includes the case where it exceeds A and is less than B.

[0016] For forming an internal electrode of an electronic component, for example, silver powder may be used. The process of manufacturing an electronic component may include a step of subjecting the silver powder to heat treatment in order to sinter the silver powder. It has been conventionally known that heat treatment causes silver ions to be generated from the silver powder and tend to diffuse into the substrate. The diffusion of silver ions generated during heat treatment is not preferable because it may lead to a short circuit between the internal electrodes.

[0017] Incidentally, silver powder may contain unavoidable impurities due to its manufacturing process. In particular, the higher the phosphorus content as an impurity, the greater the degree of silver ion generation during heat treatment, for example. The inventors of this invention wanted to suppress the diffusion of silver ions generated during heat treatment into the substrate in silver powder containing a predetermined amount of phosphorus as an impurity, and conducted research.

[0018] The technology disclosed herein provides a method for manufacturing a laminate comprising a substrate and a silver film on the substrate. This manufacturing method includes: applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A, which is a barium compound, to the substrate; and heat-treating the substrate, the silver powder applied to the substrate, and additive A to form a silver film on the substrate.

[0019] <First Embodiment> This manufacturing method includes, for example, a preparation step, an additive step, and a firing step. The preparation step is, for example, a step of preparing silver powder and additive A. In this embodiment, a silver paste is prepared in the preparation step. The silver paste contains, for example, silver powder, a resin binder, an organic solvent, and additive A.

[0020] Silver powder is a component that imparts electrical conductivity to the fired film (hereinafter also referred to as "silver film") obtained by firing silver paste. Silver powder contains, for example, 50 ppm to 500 ppm of phosphorus as an impurity. Through the inventors' research, it has been found that when silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity is subjected to heat treatment (in this case, firing treatment), silver ions are more easily generated, and the diffusion of the generated silver ions into the substrate is more likely to occur. For this reason, the composition of the silver paste disclosed herein is suitable for producing a silver film using silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity. The phosphorus content as an impurity in the silver powder may be, for example, 60 ppm or more, or 70 ppm or more. The phosphorus content as an impurity in the silver powder may be, for example, 450 ppm or less, 400 ppm or less, 350 ppm or less, 300 ppm or less, 250 ppm or less, 200 ppm or less, 180 ppm or less, 160 ppm or less, or 150 ppm. In this specification, "phosphorus content as an impurity in the silver powder" refers to the phosphorus content relative to the total silver powder. The silver powder only needs to contain a predetermined amount of phosphorus as an impurity, and may also contain other impurities (e.g., boron, calcium, chromium, copper, iron, sodium, nickel, phosphorus, silicon, zinc, etc.). Although not particularly limited, silver powder produced by the atomization method is preferably used as the silver powder. The silver content and the impurity content in the silver powder can be measured, for example, by ICP emission spectrometry.

[0021] The average particle size of the silver powder is not particularly limited and can be set appropriately depending on the application of the silver paste. For example, in applications where the silver powder is used to form internal electrodes of electronic components, the average particle size is, for example, 0.5 μm or more, preferably 1 μm or more, and more preferably 3 μm or more. By setting the average particle size within this range, for example, aggregation of silver powder in the paste can be suppressed, and the packing of silver powder in the silver film can be improved. On the other hand, the average particle size is, for example, 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 7.5 μm or less. By setting the average particle size within this range, for example, the sinterability between particles can be improved, and the resistance of the silver film can be reduced. The silver powder may include, for example, two or more groups of particles with mutually different particle size distributions. For this reason, the silver powder may be a mixed powder in which two or more groups of particles with mutually different average particle sizes are mixed. In this specification, "average particle size" refers to the 50% cumulative particle size in the particle size distribution (number-based) of the equivalent circle diameter based on electron microscope observation.

[0022] When the total amount of silver powder contained in the silver paste is considered to be 100% by mass, the content of silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity is generally 40% by mass or more, for example 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and the closer to 100% by mass, the better.

[0023] When the entire silver paste is considered as 100% by mass, the content of silver powder is, for example, 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more. This can improve, for example, the density of the silver film. When the entire silver paste is considered as 100% by mass, the content of silver powder is generally 99% by mass or less, for example 98% by mass or less, preferably 97% by mass or less, more preferably 96% by mass or less, and even more preferably 95% by mass or less.

[0024] The resin binder is a component that, for example, binds the particles constituting the silver powder together when the silver paste is applied to the substrate, and also binds the silver powder to the substrate. Preferably, the resin binder is a component that burns through during the firing of the silver paste. The type of resin binder is not particularly limited, and conventional resin binders used in this type of silver paste can be used, for example, depending on the method of applying the silver paste to the substrate.

[0025] Examples of resin binders include celluloses such as methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, and polybutyl methacrylate; epoxy resins; phenolic resins; alkyd resins; polyvinyl alcohol; polyvinyl butyral; rosins such as rosin and maleated rosin; and the like. One of the above-mentioned resin binders may be used alone, or two or more may be used in combination. When the total silver paste is considered to be 100% by mass, the content of the resin binder is generally 0.1% to 3% by mass, with 0.3% to 1% by mass being preferred.

[0026] The organic solvent is a component that dissolves or disperses, for example, silver powder, resin binder, additive A, and other components. The type of organic solvent is not particularly limited and can be selected from those that are conventionally known. The organic solvent can be used, for example, by using one type of organic solvent described below alone, or by using two or more types in appropriate combinations. Examples include alcohol-based solvents having an -OH group, ether-based solvents having an ether bond (RO-R'), ester-based solvents having an ester bond (RC(=O)-O-R'), and hydrocarbon-based solvents composed of carbon atoms and hydrogen atoms.

[0027] Examples of alcohol-based and ether-based solvents include terpineol, texanol, dihydroterpineol, benzyl alcohol, 3-methoxy-3-methyl-1-butanol, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol n-butyl ether, dipropylene glycol methyl n-propyl ether, dipropylene glycol methyl ether acetate, and dipropylene glycol methyl n-butyl ether.

[0028] Examples of ester solvents include 3-methoxy-3-methyl-1-butanol acetate, 3-methoxybutyl acetate, 1,3-butylene glycol diacetate, 1,4-butanediol diacetate, 1,6-hexanediol diacetate, propylene glycol monomethyl ether acetate, isobornyl acetate, carbitol acetate, ethyl diglycol acetate, butyl cellosolve acetate, propylene glycol diacetate, diethylene glycol monobutyl ether acetate, terpineol acetate, and dihydroterpineol acetate. Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as petroleum hydrocarbons, naphtha, dipentene, turpentine oil, and mineral spirits; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; paraffinic solvents such as normal paraffins and isoparaffins; and naphthenic solvents such as monocyclic naphthenes and bicyclic naphthenes. When the total silver paste is considered as 100% by mass, the content of the organic solvent is generally 0.5% to 10% by mass, with 2% to 7% by mass being preferred.

[0029] Additive A is a component that reacts with phosphorus, an impurity in silver powder, to form a chemically stable compound (e.g., barium phosphate). Additive A is a barium compound. The barium compound as additive A may be a barium-containing inorganic compound or an organic barium compound. Examples of barium-containing inorganic compounds include barium oxide, barium carbonate, and barium titanate. Examples of organic barium compounds include barium formate, barium acetate, barium propionate, barium stearate, barium 2-ethylhexanate, barium 2-ethylhexoxide, barium acetate, barium isopropoxide, barium ethoxide, barium 2-methoxyethoxide, barium oxalate, barium octylphenolate, barium diacrylate, barium diundecanoate, barium distearate, barium ditetracosanoate, barium dineodecanoate, barium dinonanoate, barium dipalmitate, barium diphenolate, barium diheptadecanoate, barium dilactate, barium nonylphenolate, and barium bis(12-hydroxyoctade). Examples include barium bis(2,2-dimethyloctanoate), barium bis(2-ethylhexanoate), barium bis(2-methylbenzoate), barium bis(3-methylbenzoate), barium bis(4-tertbutylbenzoate), barium bis(4-octylphenolate), barium bis(4-nonylphenolate), barium bis(4-methylbenzoate), barium bis(tertbutylbenzoate), barium bis(isobutylmaleate), barium bis(cyclohexylphenolate), barium bis(dipentyl phosphate), barium bis(dimethylhexanoate), barium bis(propane-2olate), barium dibutoxide, and barium dipropoxide.

[0030] The addition amount of additive A is preferably approximately 0.01 parts by mass to 5 parts by mass with respect to 100 parts by mass of silver powder. As the addition amount of additive A with respect to the silver powder increases, for example, the diffusion of silver ions into the substrate tends to be suppressed. From this perspective, the addition amount of additive A is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, with respect to 100 parts by mass of silver powder. On the other hand, the lower the addition amount of additive A with respect to the silver powder, the lower the resistance state of the silver film can be. From this perspective, the addition amount of additive A is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 2.5 parts by mass or less, and particularly preferably 1.5 parts by mass or less or 1 part by mass or less, with respect to 100 parts by mass of silver powder. When additive A is an organic barium compound, the addition amount in terms of barium oxide is preferably set within the above range.

[0031] The addition amount of barium with respect to 100 parts by mass of silver powder is preferably approximately 0.005 parts by mass to 3 parts by mass. As the addition amount of barium with respect to the silver powder increases, for example, the diffusion of silver ions into the substrate tends to be suppressed. From this perspective, the addition amount of barium is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, still more preferably 0.03 parts by mass or more, with respect to 100 parts by mass of silver powder. On the other hand, the lower the addition amount of barium with respect to the silver powder (for example, the lower the addition amount of additive A with respect to the silver powder), the lower the resistance state of the silver film can be. From this perspective, the addition amount of barium is preferably 2.5 parts by mass or less, more preferably 2 parts by mass or less, still more preferably 1.5 parts by mass or less or 1 part by mass or less, with respect to 100 parts by mass of silver powder. When additive A is an organic barium compound, the addition amount in terms of barium oxide is preferably set within the above range.

[0032] The addition amount M of barium with respect to 100 mol% of silver powder Ba is preferably approximately 1×10 -4 mol% to 3.0×10 -2 mol%. The addition amount M of barium with respect to the silver powder BaThe larger the value, the more likely it is to suppress the diffusion of silver ions into the substrate, for example. From this perspective, the amount of barium added M Ba This is 1.5 × 10⁻¹⁶ per 100 mol% silver powder. -4 Preferably mol% or more, 2.0 × 10 -4 More preferably mol% or more, 2.5 × 10 -4 A concentration of mol% or more is even more preferable. On the other hand, the amount of barium added to the silver powder M Ba The smaller the value (for example, the smaller the amount of additive A added to the silver powder), the lower the resistance of the silver film can be. From this perspective, the amount of barium added M Ba This is 2.5 × 10⁻¹⁶ per 100 mol% silver powder. -2 Preferably less than mol%, 2.0 × 10 -2 More preferably 1.5 × 10⁻⁶ or less, -2 More preferably 1.0 × 10% or less, -2 mol% or less or 5.0 × 10 -3 A concentration of mol% or less is even more preferable. Furthermore, when additive A is an organic barium compound, the amount added, when converted to barium oxide, should be set within the above-mentioned range.

[0033] Amount of barium added per 100 mol% silver powder (M) Ba (mol%) and the phosphorus content M when the total silver powder is considered to be 100 mol% P (mol%) ratio (M Ba / M P The ratio (M) is generally between 0.1 and 50. From the perspective of better realizing the technology disclosed herein, the ratio (M) is preferable. Ba / M P The ratio (M) is preferably 0.3 or higher, more preferably 0.5 or higher, and even more preferably 0.7 or higher. From a similar viewpoint, the ratio (M) Ba / M P ) is preferably 35 or less, more preferably 25 or less, and even more preferably 15 or less or 10 or less.

[0034] In addition to the components described above, the silver paste may contain various additives. Conventional known additives used in this type of application may be used. Examples of additives include inorganic fillers, dispersants, surfactants, viscosity modifiers, defoamers, plasticizers, antioxidants, and pigments. When the total silver paste is considered as 100% by mass, the content of additives is generally 5% by mass or less, for example, 3% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less.

[0035] The silver paste is prepared, for example, by mixing the components described above. Any conventionally known mixer used for this type of application can be used for mixing without any particular limitations.

[0036] The application step is, for example, the step of applying the silver powder prepared in the preparation step and additive A onto the substrate. In this embodiment, the application step applies the silver paste prepared in the preparation step onto the substrate. As a means of applying the silver paste, any conventionally known method used in this type of application may be employed, but for example, various printing methods such as screen printing, gravure printing, offset printing, and inkjet printing; doctor blade method; spray method; etc. are preferably used.

[0037] The firing process is a process in which, for example, after the application process, the substrate and the silver powder and additive A applied to the substrate are subjected to heat treatment (firing). In this embodiment, in the firing process, after the application process, the substrate and the silver paste applied to the substrate are subjected to heat treatment. The conditions for the heat treatment (firing) are not particularly limited and can be set as appropriate depending on the application of the laminate. The temperature of the heat treatment should be set to a temperature at which, for example, the organic components in the silver paste burn out and the silver powder sintersects. The temperature of the heat treatment can be set to, for example, 500°C to 1000°C (for example, 600°C to 800°C). The time of the heat treatment should be set to, for example, 30 minutes to 10 hours. The atmosphere during the heat treatment should be, for example, an air atmosphere or an inert atmosphere such as a nitrogen atmosphere or a noble gas atmosphere.

[0038] The above describes one embodiment of the method for manufacturing the laminate disclosed herein. In this embodiment, the application process involves applying a silver paste containing silver powder, a resin binder, an organic solvent, and additive A onto a substrate. As mentioned above, the silver powder used here contains a predetermined amount of phosphorus as an impurity, so silver ions are generated by heat treatment (calcination treatment) and easily diffuse into the substrate, for example. In contrast, by including additive A, which is a barium compound, in the silver paste, a chemically stable compound (for example, barium phosphate) is formed. Therefore, the diffusion of silver ions generated by heat treatment into the substrate is suitably suppressed. In addition, since silver paste is used in the application process, a simpler process of mixing each raw material can be adopted in the preparation process. Therefore, according to the configuration of the first embodiment, the effect of improving the productivity of silver films can also be realized.

[0039] The manufacturing method for the laminate disclosed herein is not limited to the embodiments described above. For example, this manufacturing method may include any steps in addition to the steps described above. This manufacturing method may include, for example, a drying step, a pressing step, etc., as needed. The drying step is, for example, a step of volatilizing the organic solvent in the silver paste, and is preferably carried out between the application step and the firing step. The drying conditions are not particularly limited and can be appropriately set depending on the type and amount of organic solvent used. The pressing step is, for example, a step of pressing the silver powder applied to the substrate, and is preferably carried out between the application step and the firing step. The pressing conditions are not particularly limited and can be appropriately set depending on the application of the laminate, the desired thickness of the silver film, etc.

[0040] <Second Embodiment> In the first embodiment described above, silver paste was applied in the application step. However, in the manufacturing method disclosed herein, it is sufficient that silver powder and additive A are applied in the application step, and the applied substance is not limited to silver paste.

[0041] In the second embodiment, coated silver powder is prepared in the preparation step. The coated silver powder here comprises silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity, and a coating portion on the surface of the silver powder containing additive A. The procedure for preparing the coated silver powder is not particularly limited, but for example, a method of mixing silver powder and additive A may be employed. Here, first, silver powder, additive A, and an organic solvent are prepared. As the silver powder, the silver powder described in the first embodiment may be used. As additive A, additive A described in the first embodiment may be used, but among them, an organic barium compound is preferably used. As the organic solvent, additive A described in the first embodiment may be used, but among them, an alcohol such as ethanol is preferably used.

[0042] Next, the silver powder, additive A, and organic solvent are mixed. For example, a first mixture of additive A and the organic solvent may be prepared first, and then the silver powder is added to the first mixture and mixed further to prepare a second mixture. During the mixing after adding the silver powder, it is preferable to apply ultrasonic energy to the material. The conditions for applying ultrasonic energy are not particularly limited and can be set as appropriate. Then, the obtained second mixture can be dried, heat-treated, pulverized, classified, etc., as needed to obtain coated silver powder.

[0043] In this embodiment, the coating silver powder is applied to the substrate during the application process. Then, the coated silver powder applied to the substrate is subjected to heat treatment (sintering treatment) to produce a laminate.

[0044] As described above, in this embodiment, the manufacturing method involves applying coated silver powder, which comprises silver powder and a coating portion containing additive A on the surface of the silver powder, onto a substrate. In other words, in this embodiment, coated silver powder in which the silver powder and additive A are integrated is used. Therefore, the diffusion of silver ions into the substrate can be suppressed more efficiently.

[0045] Regarding the second embodiment, matters other than those described herein are the same as those of the first embodiment. Therefore, further explanation is omitted here.

[0046] The technology disclosed herein provides a method for manufacturing electronic components. The method for manufacturing electronic components may include manufacturing a laminate using the laminate manufacturing method described above. Although not particularly limited, the laminate manufacturing method described above is preferably used to form electrodes for electronic components such as inductance components and capacitor components. The laminate manufacturing method described above has the effect of suppressing the diffusion of silver ions into the substrate. Therefore, by including such a laminate manufacturing method, it is possible to provide electronic components in which the diffusion of silver ions into the substrate is suppressed. In such electronic components, for example, the risk of internal short circuits is better reduced.

[0047] The following describes a multilayer chip inductor, an example of an electronic component. Figure 1 is a schematic cross-sectional view of multilayer chip inductor 1. Note that the dimensional relationships (length, width, thickness, etc.) in Figure 1 do not necessarily reflect the actual dimensional relationships. The symbols X and Z in the drawing represent the left-right and up-down directions, respectively. However, this is merely a directional distinction for the sake of explanation.

[0048] The size of the multilayer chip inductor 1 shown in Figure 1 is not particularly limited, but it is preferable to have sizes such as 1608 shape (1.6 mm × 0.8 mm) or 2520 shape (2.5 mm × 2.0 mm). The multilayer chip inductor 1 comprises a main body 10 and external electrodes 20.

[0049] The multilayer chip inductor 1 comprises a main body 10 and external electrodes 20 provided on both sides of the main body 10 in the left-right direction X. In the main body 10, for example, a plurality of magnetic material layers 12 are stacked in the vertical direction Z and integrated with each other. Examples of materials constituting the magnetic material layers 12 include ferrite magnetic materials such as Ni-Cu-Zn ferrite; Fe-Cr-Si alloy; Fe-Al-Si alloy; Fe-Si-M soft magnetic alloy (where M is at least one of chromium, aluminum, and titanium); and other metallic materials.

[0050] Between each magnetic layer 12, a coil conductor is provided as an internal electrode layer 14. In this embodiment, the coil conductor is a fired film of the silver paste disclosed herein or the coated silver powder disclosed herein. Two coil conductors adjacent to each other in the vertical Z direction, with the magnetic layer 12 in between, are electrically connected through via holes provided in the magnetic layer 12. As a result, the internal electrode layer 14 is configured in a three-dimensional coil shape (helical). Both ends of the coil conductor are connected to the external electrodes 20.

[0051] A multilayer chip inductor 1 can be manufactured, for example, by the following procedure. First, a magnetic paste containing a metal material constituting the magnetic layer 12, a binder, and an organic solvent is prepared and supplied onto a carrier sheet to form a green sheet. Next, the green sheet is rolled and dried. Then, the green sheet is cut to a desired size to obtain a plurality of magnetic layer forming sheets. Next, via holes are formed at predetermined positions on these magnetic layer forming sheets using a drill or the like. Next, the silver paste disclosed herein is printed in a predetermined coil pattern at predetermined positions on the plurality of magnetic layer forming sheets and dried. Then, these are laminated and pressed together to produce a laminate of unfired green sheets. By firing this, the green sheets are fired integrally, and a body 10 comprising a magnetic layer 12 and an internal electrode layer 14 is formed. Finally, an external electrode forming paste is applied to both ends of the body 10 and fired to form external electrodes 20. In this way, a multilayer chip inductor 1 can be manufactured.

[0052] As described above, the technology disclosed herein provides a method for manufacturing a laminate comprising a substrate and a silver film on the substrate. This manufacturing method includes applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity and additive A, which is a barium compound, to the substrate, and heat-treating the substrate, the silver powder applied to the substrate, and additive A to form a silver film on the substrate.

[0053] The silver powder used in the manufacturing method disclosed herein contains 50 ppm to 500 ppm of phosphorus as an impurity. When silver powder contains phosphorus, which has high electronegativity, electrons in the silver electron cloud are attracted to the phosphorus, for example, causing an uneven distribution of electrons and making it easier for silver ions to be generated. In addition, when heat is applied to the silver powder, impurities tend to move to the surface of the silver powder. When silver powder is heat-treated (calcined), the movement of impurities to the surface of the silver powder makes it easier for silver ions to diffuse from the surface of the silver powder into the substrate. For this reason, silver powder containing phosphorus is inherently prone to the diffusion of silver ions into the substrate due to calcination.

[0054] In contrast, this manufacturing method uses additive A, which is a barium compound, along with silver powder. When barium compounds react with phosphorus, they form, for example, chemically stable barium phosphate. Therefore, when silver powder and additive A are applied together to a substrate, during heat treatment, the impurity phosphorus reacts with additive A to form chemically stable barium phosphate. Thus, because additive A can form a chemically stable compound with phosphorus, in the process of forming a silver film (fired film) by heat treatment of silver powder containing a predetermined amount of phosphorus, the uneven distribution of electrons in silver is suppressed, and the diffusion of silver ions from the silver powder to the substrate can be suppressed.

[0055] The following describes test examples related to the technology disclosed herein, but it is not intended to limit the technology disclosed herein to these test examples.

[0056] <Test 1> -Example 11- In Test 1, silver powder A was prepared, with an average particle size of 5 μm and a phosphorus concentration of 146 ppm. Ethyl cellulose was used as the resin binder. Diethylene glycol monobutyl ether acetate was used as the organic solvent. Barium titanate was used as an additive. The phosphorus concentration of silver powder A was measured using an ICP spectrometer (PS3520VDDII, manufactured by Hitachi High-Tech Corporation).

[0057] Silver powder A, a resin binder, an organic solvent, and an additive were mixed using a mixing device to produce a silver paste. Here, when the total amount of silver powder A, resin binder, and organic solvent was considered to be 100% by mass, the content of silver powder A was 95% by mass, the content of resin binder was 0.5% by mass, and the content of organic solvent was 4.5% by mass. The amount of additive was 1 part by mass per 100 parts by mass of silver paste. Next, the silver paste was dried, and the dried paste was pulverized to obtain paste powder. Then, using a uniaxial molding machine (a hydraulic press PHK5-S manufactured by Towa Seiki Co., Ltd.), the paste powder was filled into a mold and pressurized along the axial direction at a pressure of 78 MPa to obtain cylindrical pellets of paste powder with a diameter of 8 mm. Next, the pellets were placed on a glass substrate ("S7213" manufactured by Matsunami Glass Industry Co., Ltd.) and heat-treated in a belt furnace at 700°C for 0.5 hours in an atmospheric environment.

[0058] On the glass substrate after heat treatment, a ring-shaped discolored area was formed surrounding the periphery of the pellet. This discoloration originated from silver ions diffused from the pellet into the glass substrate. Here, the diameter of the combined portion of the pellet and the discolored area (hereinafter also referred to as the "diffusion diameter") was measured. Then, the following equation (A): Diffusion rate (%) = {(diffusion diameter - pellet diameter) / pellet diameter} × 100 (A) Based on this, the diffusion rate (%) of silver ions from the pellet was calculated. The results are shown in the corresponding column of Table 1.

[0059] -Examples 12-15- The compounds shown in Table 1 were used as additives. Otherwise, the pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion rate was calculated. In Example 12, a "-" in the "Additives" column of Table 1 indicates that no additives were added.

[0060] -Examples 16-18- Silver powder B, with an average particle size of 5 μm and a phosphorus concentration of 70 ppm, was used as the silver powder. Copper powder was used as an additive in the amount indicated in the "Amount Added (parts by mass)" column of Table 1. Otherwise, pellets for each example were prepared using the same materials and procedure as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 1. Note that for Example 16, a "-" in the "Additives" column of Table 1 indicates that no additive was added.

[0061] [Table 1]

[0062] Regarding Examples 11 to 18, the compounds (additives) added to the paste in each example can form a coating on the surface of the silver powder. From the results shown in Table 1 for Examples 11 to 18, it was found that by using the coated silver powder of Example 11, which includes silver powder and a coating on the surface of the silver powder containing a barium compound (in this case, barium titanate), the diffusion of silver ions into the substrate (in this case, a glass substrate) due to firing can be suppressed.

[0063] <Exam 2> -Examples 21-24- A mixed powder of silver powder A and silver powder C was prepared as the silver powder. Silver powder C was a silver powder with an average particle size of 1.5 μm and a phosphorus concentration of 0 ppm. The mixing ratio (mass ratio) of silver powder A to silver powder C in the mixed powder (silver powder A:silver powder C) was 70:30. Ethyl cellulose was prepared as the resin binder. Diethylene glycol monobutyl ether acetate was prepared as the organic solvent. Barium carbonate was used as an additive in the amount indicated in the "Amount Added (parts by mass)" column of Table 2. Otherwise, pellets for each example were prepared using the same materials and procedures as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 2. Note that for Example 21, the "-" in the "Additives" column of Table 2 indicates that no additive was added. For reference, Figure 2 shows an image of Example 21. Figure 3 shows an image of Example 24.

[0064] [Table 2]

[0065] Regarding Examples 21 to 24, the results shown in Table 2 indicate that by using the coated silver powders of Examples 22 to 24, which include silver powder and a coating portion containing a barium compound (in this case, barium carbonate) on the surface of the silver powder, the diffusion of silver ions into the substrate (in this case, a glass substrate) due to firing can be suppressed.

[0066] <Exam 3> -Examples 31A to 31E- Barium-2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of barium oxide added matched the amount shown in the "Addition Amount (parts by mass)" column of Table 3. Otherwise, the pellets for each example were prepared using the same materials and procedure as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 3.

[0067] -Example 32A~Example 32C- Magnesium 2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of magnesium oxide added matched the amount shown in the "Addition Amount (parts by mass)" column of Table 3. Otherwise, the pellets for each example were prepared using the same materials and procedure as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 3.

[0068] -Example 33A~Example 33C- Calcium 2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of calcium oxide added matched the amount shown in the "Addition Amount (parts by mass)" column of Table 3. Otherwise, the pellets for each example were prepared using the same materials and procedure as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 3.

[0069] -Examples 34A to 34C- Strontium-2-methoxyethoxide was prepared as an additive. This additive was used so that the amount of strontium oxide added matched the amount shown in the "Addition Amount (parts by mass)" column of Table 3. Otherwise, the pellets for each example were prepared using the same materials and procedure as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 3.

[0070] -Example 35A~Example 35C- A mixed powder of silver powder B and silver powder C was prepared as the silver powder. The mixing ratio (mass ratio) of silver powder B to silver powder C in the mixed powder (silver powder B:silver powder C) was 70:30. Barium 2-methoxyethoxide was used as an additive, so that the amount of barium oxide added matched the amount shown in the "Addition Amount (parts by mass)" column of Table 3. Otherwise, pellets for each example were prepared using the same materials and procedure as in Example 11, and the diffusion rate was calculated. The results are shown in the corresponding column of Table 3. Note that for Example 35C, a "-" in the "Additives" column of Table 3 indicates that no additive was added.

[0071] [Table 3]

[0072] Regarding Examples 31A to 31E, 32A to 32C, 33A to 33C, 34A to 34C, and 35A to 35C, the results shown in Table 3 indicate that by using the coated silver powders of Examples 31A to 31E, 35A, and 35B, which include silver powder and a coating portion containing a barium compound (in this case, a compound derived from an organic barium compound) on the surface of the silver powder, the diffusion of silver ions into the substrate (in this case, a glass substrate) due to firing can be suppressed.

[0073] <Exam 4> -Examples 41-43- Barium-2-methoxyethoxide, silver powder A, and alcohol (ethanol) as an organic solvent were placed in a mixer and stirred for 10 minutes while applying ultrasonic energy. The amount of barium-2-methoxyethoxide was equal to the amount of barium oxide added, as indicated in the "Amount Added (parts by mass)" column of Table 4. The amount of silver powder A was 10 g. The amount of alcohol (ethanol) was 1.5 g. Next, the mixture was dried at 70°C to evaporate the organic solvent. The powder obtained after drying was ground using a mortar and pestle to obtain coated silver powder for each example. Using a uniaxial molding machine, the obtained silver powder (0.4 g) was filled into a mold and pressurized at a pressure of 78 MPa along the axial direction to obtain cylindrical pellets with a diameter of 8 mm. Next, the pellets were subjected to the same heat treatment as in Example 11. Then, the diffusion rate of each example was determined using the same method as in Example 11. The results are shown in the corresponding column of Table 4.

[0074] -Example 44- No additives were used. Except for this, the pellets for this example were prepared using the same materials and procedures as in Examples 41-43, and the diffusion rate was calculated. Note that a "-" in the "Additives" column of Table 4 indicates that no additives were added. The results are shown in the corresponding column of Table 4.

[0075] [Table 4]

[0076] Regarding Examples 41 to 43, according to Test 4, by mixing silver powder A and barium (methoxyethoxyethoxide) under the above conditions, barium (methoxyethoxyethoxide) adheres to the surface of silver powder A. From the results shown in Table 4, it was found that by using the coated silver powders of Examples 41 to 43, which include silver powder and a coating portion containing a barium compound (in this case, a compound derived from an organic barium compound) on the surface of the silver powder, the diffusion of silver ions into the substrate (in this case, a glass substrate) due to firing can be suppressed.

[0077] The technologies disclosed herein may include the following: Section 1: A method for manufacturing a laminate comprising a substrate and a silver film on the substrate, The process involves applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity, and additive A, which is a barium compound, to the substrate. The above-mentioned substrate, the silver powder applied to the substrate, and the additive A are subjected to heat treatment to form a silver film on the substrate. A manufacturing method that includes this. Section 2: The manufacturing method according to item 1, wherein the application includes applying a silver paste containing the silver powder, a resin binder, an organic solvent, and the additive A onto the substrate. Section 3: The manufacturing method according to item 2, wherein the additive A comprises at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate. Section 4: The manufacturing method according to claim 1, wherein the application includes applying coated silver powder, which comprises the silver powder and a coating portion containing the additive A on the surface of the silver powder, onto the substrate. Section 5: The manufacturing method according to item 4, wherein the additive A is an organic barium compound. Item 6: The manufacturing method according to any one of items 1 to 5, wherein, in the application described above, 0.03 parts by mass or more and 3 parts by mass or less of additive A is used per 100 parts by mass of the silver powder. Section 7: A method for manufacturing electronic components, comprising manufacturing the laminate using the manufacturing method described in items 1 to 6. Section 8: It is a silver paste, It contains silver powder containing phosphorus in amounts between 50 ppm and 500 ppm as an impurity, a resin binder, an organic solvent, and additive A. Here, additive A is a barium compound, a silver paste. Section 9: The silver paste according to claim 8, wherein the additive A comprises at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate. Section 10: The silver paste according to item 8 or 9, comprising 0.03 parts by mass or more and 3 parts by mass or less of additive A per 100 parts by mass of the silver powder. Section 11: Silver paste used in the manufacture of electronic components, as described in any one of items 8-10. Section 12: Coated silver powder, Silver powder containing phosphorus in amounts between 50 ppm and 500 ppm as an impurity, A coating portion containing a barium compound on the surface of the silver powder, A coated silver powder comprising the following features. Section 13: The barium compound is an organic barium compound, as described in item 12, which is the coated silver powder. Section 14: Silver-coated powder as described in item 12 or 13, used in the manufacture of electronic components. [Explanation of Symbols]

[0078] 1. Multilayer chip inductor 10 Main Unit 12 Magnetic layer 14 Internal electrode layer 20 External Electrodes

Claims

1. A method for manufacturing a laminate comprising a substrate and a silver film on the substrate, The process involves applying silver powder containing 50 ppm to 500 ppm of phosphorus as an impurity, and additive A, which is a barium compound, to the substrate. The substrate, the silver powder applied to the substrate, and the additive A are subjected to heat treatment to form a silver film on the substrate. A manufacturing method that includes this.

2. The manufacturing method according to claim 1, wherein the application includes applying a silver paste containing the silver powder, a resin binder, an organic solvent, and the additive A onto the substrate.

3. The manufacturing method according to claim 2, wherein the additive A comprises at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate.

4. The manufacturing method according to claim 1, wherein the application includes applying coated silver powder, which comprises the silver powder and a coating portion on the surface of the silver powder containing the additive A, onto the substrate.

5. The manufacturing method according to claim 4, wherein the additive A is an organic barium compound.

6. The manufacturing method according to claim 1, wherein, in the application described above, 0.03 parts by mass or more and 3 parts by mass or less of additive A is used per 100 parts by mass of the silver powder.

7. A method for manufacturing an electronic component, comprising manufacturing the laminate using the manufacturing method described in claims 1 to 6.

8. It is a silver paste, It contains silver powder containing phosphorus at a concentration of 50 ppm to 500 ppm as an impurity, a resin binder, an organic solvent, and additive A. Here, additive A is a barium compound, a silver paste.

9. The silver paste according to claim 8, wherein the additive A comprises at least one of an organic barium compound, barium oxide, barium titanate, and barium carbonate.

10. The silver paste according to claim 8 or 9, comprising 0.03 parts by mass or more and 3 parts by mass or less of additive A per 100 parts by mass of the silver powder.

11. A silver paste according to claim 8 or 9, used in the manufacture of electronic components.

12. Coated silver powder, Silver powder containing phosphorus in amounts of 50 ppm to 500 ppm as an impurity, A coating portion containing a barium compound on the surface of the silver powder, A coated silver powder comprising the following features.

13. The coated silver powder according to claim 12, wherein the barium compound is an organic barium compound.

14. A coated silver powder according to claim 12 or 13, used in the manufacture of electronic components.

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